Half Full Or Half Empty? Either Way it's Time to Plan

(June 2006, Perri Standish-Lee, et. al. for Journal AWWA)

MANAGING WATER QUALITY AND QUANTITY FOR SUSTAINABILITY ASSUMES SPECIAL SIGNIFICANCE WHERE WATER RESOURCES ARE SCARCE.

William Shakespeare wrote in Henry VI, "smooth runs the water where the brook is deep." Unfortunately, life is not so smooth where water supply is scarce, and utilities that are responsible for sustaining water resources in arid and semi-arid regions face turbulent times. Effective management of both water quality and quantity are especially critical for communities furnished with the short end of the divining rod.

WESTERN UNITED STATES FACES DROUGHT CONCERNS
Arid and semi-arid regions comprise approximately 40% of the earth's surface area and sustain more than one billion people but experience only 2% of the global runoff (UNEP, 2000). In the United States, several consecutive years of abnormally high temperatures, below-average precipitation, and increased water demands left the Colorado River at an all-time low in 2004 (USBR, 2004). Water surface levels in reservoirs throughout the western United States, such as Lake Powell and Lake Mead, are currently at near-record lows. Additional precipitation during 2005 led to hopes of alleviating this drought; however, above-average temperatures and below-normal precipitation in recent months have refuelled drought concerns.

Aggravating the situation is the decline in water quality that results from diminished flows. In the Colorado River Basin and in much of the West, salinity concentrations in rivers and streams are directly influenced by flow volume. Figure 1 illustrates how salinity concentrations in the Colorado River dropped in the mid-1980s when river flows were at historically high levels and, conversely, in the early 1990s when flows were low and salinity concentrations were high (Colorado River Basin Salinity Control Forum, 2005).

The Sierra Nevada are an important source of water supply for much of the western United States. The snowpack from these mountains can be visualized as a thermal storage reservoir, retaining snow that eventually melts and provides water during the spring and summer months. However, even in Northern California where water resources are relatively more abundant than in Southern California, climate changes could have a profound effect on water availability. Although total annual precipitation values are predicted to remain relatively stable, most climate change models predict diminished snowpack levels in the Sierra Nevada (Cayan et al, 2001). Figure 2 compares recent snowpack conditions with projected conditions for the year 2060.

With a reduced snowpack, meeting water supply demands during dry seasons would become more difficult. Some models predict higher flows during the rainy season and lower flows during the dry season. In the dry season, problems of reduced supply are likely to be exacerbated by declining water quality resulting from diminished flows. In the San Francisco Bay estuary, for example, such changes would yield much higher dry-season salinities and elevated bromide concentrations (Figure 3).

STRATEGIES VITAL TO LONG-TERM WATER SUPPLY
Existing water resources must be sustained to meet water demands of the urban, industrial, and agricultural sectors, which compete for limited supplies. Sustainability in all three sectors requires effective utilization of water supplies, including implementation of water-saving practices and development of emergency water shortage/drought plans. It requires communities and water agencies to work together to optimize existing water sources without affecting future generations' abilities to do the same. Examples of some entities cooperating to achieve sustainability are:

• In the 1970s, the seven states of the Colorado River Basin implemented a salinity control program that is believed to be an important factor in having reduced the overall Colorado River salinity by as much as 100 mg/L (Colorado River Basin Salinity Control Forum, 2005).
• The Contra Costa Water District's construction of Los Vaqueros Reservoir allows high-quality water to be pumped into the reservoir in spring months when the Sierra Nevada snowpack melts and flows into the delta. This water acts as a reserve for late summer months when the salinity levels in the delta are high because of low river flows.

Strategies for helping achieve water sustainability in arid regions include:

• technology transfer;
• public outreach;
• conservation and other activities that increase water use efficiency;
• quantification of effective as well as ineffective water management practices;
• assessment of potential future supplies; and

Identification of practical and acceptable water supply options has become a fundamental element of water strategy development. Technological progress and regulatory changes throughout the past decade have opened numerous water supply options that were once considered infeasible because of exorbitant costs or health concerns. Supply options that should be considered in the development of successful sustainability strategies include:

• water conservation;
• reuse of treated wastewater and stormwater;
• desalination of ocean and brackish waters;
• stormwater detention;
• water transfers, water banking, or aquifer storage and recovery; and
• out-of-basin importation of water supplies to basins in need.

The ultimate choice of any supply option should be driven by the option's ability to provide water of suitable quality and to function as a long-term source of supply.

UTILITIES PLAN FOR THE FUTURE
Emerging regulations are becoming more stringent. Water utilities with superior water quality are able to meet the regulations with minimal changes to their treatment systems. However, utilities that rely on degraded water sources are finding it necessary to upgrade treatment systems and/or adopt new sources of supply, both of which can be quite costly.

New policies and practices that encourage conservation offer hope for parched communities, especially those in arid climates that are hardest hit by drought. Some water demand-management measures-such as restricting the planting of high water-demand crops and encouraging water friendly landscaping in both the public and private sectors-generate substantial water savings. Incorporation of water-saving devices in households yields smaller but equally important savings.

The introduction of measures intended to reduce water demand often arises from ad hoc analysis and decisions by governments at times of extreme water shortage. Water utilities in the West and Southwest are beginning to develop water strategies and master plans that effectively and proactively incorporate water demand-management measures, as well as technologies and practices to address water quality issues. The Southern Nevada Water Authority (SNWA) in Las Vegas, Nev., and the Zone 7 Water Agency in Livermore, Calif., offer two examples.

SNWA. The SNWA implemented plans to manage, protect, and augment the local water supply, which primarily depends on Colorado River water delivered from Lake Mead. First, in 1996, the SNWA implemented a comprehensive water resource plan that outlined a portfolio of existing and future resource options to help meet future demands (SNWA, 2005). The original plan, which has been reviewed annually, emphasized water conservation, environmental protection, and the need for flexibility in the timing and implementation of additional resources and associated treatment and delivery infrastructure. That plan launched a series of regional water conservation programs to achieve 25% regional conservation by the year 2010.

When surface water levels in Lake Mead began to drop in early 2000 as a result of the severe drought in the Colorado River Basin (Figure 4), the SNWA also adopted a comprehensive regional drought plan to accelerate local water conservation and mitigate potential water shortages. Through conservation initiatives and subsequent drought plan measures, Southern Nevada's annual water consumption has decreased during the past three years by approximately 20 bil gal, despite the addition of nearly 250,000 new residents and 38 million annual visitors.

Additionally, in 2004 the SNWA implemented two plans to accelerate the development of three water resource projects to provide additional groundwater and surface water resources to Southern Nevada. This work included the initiation of an integrated water planning process-involving all relevant parties-to assess funding and develop alternatives for proposed projects (SNWA, 2005).

To augment its existing surface water rights to Lake Mead, the SNWA has begun to develop two other smaller, local surface water sources. In addition, the utility is expanding its water rights in other areas, establishing water banking programs within the Las Vegas Valley and in Arizona and California, reusing water supplies for non-potable purposes, and returning highly treated wastewater flows to the Colorado River for return-flow credits. Throughout these planning efforts, the SNWA has worked closely with local and regional stakeholders to identify solutions that maximize the benefits to all stakeholders.

Zone 7 Water Agency. The Zone 7 Water Agency, which is developing strategies to address water quality issues associated with reduced freshwater flows in the San Francisco Bay estuary, serves as another example of a major utility planning for the future of its water supply. Zone 7's salt-management strategy, developed to address increasing levels of total dissolved solids in the groundwater basin, supports increased conjunctive use with shallow groundwater demineralization to offset current and future salt-loading to the main groundwater basin. In addition, Zone 7 is adding a new surface water treatment plant to address long-term water quality concerns and respond to short-term concerns such as taste and odor, total organic carbon, and high bromide concentrations from the South Delta that occur during droughts. The Altamont Water Treatment Plant will incorporate coagulation, membrane filtration, ozonation, and biologically activated contact to reduce activated organic carbon. During periods of high bromide concentrations, an application of acid, ammonia, or chlorine will be used before ozonation to reduce bromate formation.

COLLABORATION AND COMMITMENT ARE KEY
As population growth, climate change, and water quality degradation further affect the limited water resources of the western United States, local governments, water utilities, and the public must continue their efforts to sustain supplies. The human population can contend with water scarcity only through responsible development, effective water resource management, and the realization that the world shares the same finite water supply.

ABOUT THE AUTHORS
Perri Standish-Lee (to whom correspondence should be addressed) is the director of integrated watershed planning with Black & Veatch Corp., 8950 Cal Center Dr., Ste. 238, Sacramento, CA 95826; (916) 361-1282; standish-leepp@bv.com. She is also the specialist group chairman for the International Water Association's River Basin and Watershed Management Specialist Group. Standish-Lee has more than 30 years of experience in the evaluation of source water quality, including surface water and groundwater supplies, water treatment processes, and watershed management. She has a BS degree in chemistry/biochemistry from the Israel Institute of Technology in Haifa, Israel, and an MS degree in environmental engineering from Arizona State University in Tempe. Erik Loboschefsky is a graduate student at the University of California-Davis and a junior engineer for Black & Veatch. Kristina Lecina is a water resources engineer with Black & Veatch.

REFERENCES

Cayan, D. M. et al, 2001. Investigation of Climate Change Impacts on Water Resources in the California Region: Department of Energy Accelerated Climate Prediction Initiative (ACPI) Progress Report. Scripps Institution of Oceanography, San Diego.

Colorado River Basin Salinity Control Forum, 2005. 2005 Review: Water Quality Standards for Salinity, Colorado River System. Colorado River Basin Salinity Control Forum, Bountiful, Utah.

SNWA (Southern Nevada Water Authority), 2005. SNWA Resource Plan. www.snwa.com/html/wr_resource_ plan.html (accessed April 2006).

UNEP (United Nations Environment Programme), 2000. The Watershed: Water From the Mountains Into the Sea. www.unep.or.jp/ietc/Publications/Short_Series/LakeReservoirs-2/index.asp (accessed April 2006).

USBR (US Bureau of Reclamation), 2004. USBR Lower Colorado Region. www.usbr.gov/lc (accessed April 2006).

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